Why Does the Coolant Keep Decreasing?

[McKai]

There are three main reasons for coolant loss: 1. Excessive natural consumption: Engine oil or cooling system issues causing excessively high engine temperatures, leading to increased coolant consumption. Solution: Use high-quality engine oil and regularly inspect the vehicle's cooling system. 2. Coolant entering the cylinders: Damaged intake manifold gaskets or cylinder head gaskets can allow coolant to enter the combustion chambers where it evaporates. Solution: Replace the faulty components. 3. Radiator cap, radiator, or water pump leaks: Visible coolant leaks can often be identified by water stains under the chassis or radiator. Solution: Replace the damaged radiator cap, radiator, or water pump as needed.

[VanNadia]

I've also experienced the issue of coolant constantly running low, which was quite worrisome at the time. Unexplained coolant loss should be investigated from several angles: First, external leaks—common trouble spots include radiator seams, water pump seals, or aging hoses. Carefully check the undercarriage for any signs of seepage. Second, internal leaks—such as a blown head gasket allowing coolant to enter the oil passages, turning the oil milky like milk tea, with white smoke from the exhaust. Third, normal evaporation loss—especially after using AC in summer, losing about 50ml per month is within normal range. Later, I had the repair shop perform a pressure test and discovered a cracked plastic seam on the radiator. If you notice continuous fluid level drops, investigate promptly—engine overheating and cylinder scuffing could become serious trouble.

[HarmonyDella]

In the past, the coolant in my car would often mysteriously decrease, and it took me a long time to figure out the reason. The most common issue is pipe leakage—small spots like the welds on the radiator, water pump seals, or heater core can slowly seep. When starting the car cold, check underneath for any water stains. Another reason is aging rubber hoses—after ten years, those hoses became as brittle as tree bark, cracking at the slightest touch. An easily overlooked cause is a faulty pressure relief valve in the coolant reservoir cap, which can cause coolant to evaporate under high pressure. Internal engine problems are also worth noting—if there are cracks in the cylinder block or a damaged head gasket, coolant can leak into the combustion chamber, causing white smoke from the exhaust pipe. Never just top up with water if the coolant is low, as mineral deposits can clog the pipes.

[DelKaden]

There are three possible reasons for continuous coolant loss: external leakage, internal leakage, or natural consumption. External leakage can be identified by checking for cracks or seepage in pipes and the radiator—parking the car and observing water stains on the ground is the most straightforward method. Internal leakage is particularly troublesome, as engine damage can cause coolant to mix with engine oil or enter the cylinders, turning the oil milky white. Natural consumption is minimal, requiring no more than 200ml top-up every 20,000km. Last time I dealt with this, I focused on three key areas: aging rubber seals at radiator connections, pinhole leaks in the heater core, and a faulty pressure valve in the radiator cap. Remember to use the same color coolant when topping up—mixing different types can cause crystallization and blockages. Prolonged coolant deficiency can lead to overheating, so early investigation is advisable for peace of mind.